Nanoscale structures are becoming increasingly important because they provide the basis for devices with dramatically reduced power and mass, while simultaneously having enhanced capabilities, and previous patent applications have disclosed the advantageous use of such nanostructures in a number of different real-time, molecule specific sensors.
However, assembling large numbers of nanoscale structure in predetermined ways is notoriously difficult. For example, conventional nanoscale structures are arranged by patterning a substrate using e-beam lithography, which, while effective, is time-consuming and expensive. In addition, e-beam lithography requires the use of a limited number of well-defined, rigid substrate materials.
To solve these problems a number of recent publications have suggested the use of “capillarity-driven” assembly of groups of nanotubes. In such a system the dispersion and evaporation of a fluid on a dense mat of nanotubes drives the rearrangement and patterning of the nanotubes on the substrate surface. However, the current methods still fundamentally rely on patterning the substrate to “control” the capillarity-driven effect, and the ultimate nanostructure. For example, Chakrapani, et al. describe the results of capillarity-driven forces on already patterned nanotube structures. (See, e.g., Chakrapani, et al.; PNAS, vol. 101(12), pg. 4009-12 (Mar. 3, 2004)) Likewise, Liu, et al. discuss the use of “laser-etched” carbon nanotube surfaces to drive capillarity-driven effects to form highly controlled carbon nanotube structures. (Liu, et al., Angew. Chem. Int. Ed., vol. 43, pg. 1146-49 (2004)) In both of these results the investigators indicated that, if left alone, the capillary-driven forces would produce consistently irregular or irreproducible nanotube structures. As such, these methods still require the use of time-consuming and expensive lithography techniques to ensure the controlled growth of specific two-dimensional carbon nanotube formations.
Accordingly, a need exists for an improved method for inexpensively and controllably forming patterned nanoscale structures.